Fluid Lines And Fittings Flashcards
What are the two types of fluid lines commonly found in aircraft?
Rigid metal lines
Flexible hoses
What are aircraft plumbing lines usually made of?
Metal tubing
Flexible hose
Fittings
Describe the method of classifying metal tube according to size.
Metal tubing is sized according to wall thickness and outside diameter.
Outside diameter is measured in 1/16th inch increments
When installing stainless steel tubing, what type of fittings should be used?
Stainless steel fittings
What is the function of the sleeve on a flare-tube fitting?
The nuts fit over the sleeve and draws the sleeve and tubing flare tightly against the male fitting to form the seal
Describe the two types of flares commonly used on aircraft tubing
Single flare
Double flare
How can you determine if a fitting is an AN type rather than an AC type?
AN fittings have a shoulder between the flare cone and the end of the threads
AC Fittings do not
What are the most significant differences between AN and AC fittings?
AN fittings have sleeve length, thread pitch, shoulder between threads, and a flare cone
How are standard AN and AC type fluid line fittings identified?
AN fluid lines
Colored either blue or black
Coarser threads, smaller shoulder between threads
37 degree cone
AC type fluid lines
Colored either gray or yellow
Completely threaded all the way to the 35 degree cone
What are the names of the parts of a flareless tube fitting?
Nut
Ferrule
Sleeve
How do you tell a flareless fitting from a flare type fitting?
Flareless fittings don’t have a flare cone and there is no space between the threads and the end of the fitting
What is the effect of overtightening a flare-type fitting?
The sealing surface may be damaged or the flare cut off
In addition to being securely clamped, what is an additional requirement for installing metal fuel, oil, and hydraulic lines?
The lines must be electrically bonded to the structure
What is the advantage of a flexible Teflon hose over a regular hose?
Teflon hoses have a better resistance to chemicals
Higher strength properties at higher temps
Describe the identification markings commonly found on flexible hoses
Lay line Mil spec number (identification) Manufacturers name or symbol Hose size Date code
What type of information is on a hose lay line?
Type of hose
Quarter/year of manufacture
How can you determine if a flexible hose has been correctly/incorrectly installed?
Lay line will be straight if properly installed
Twisted lay line indicates incorrect installation
What is the purpose of the identification stripe running along the length of a flexible hose?
Stripe is called a lay line and indicates if the hose has twisted during installation
How are flexible hose sizes designated?
By inside diameter, measured in 1/16th inch increments
What precautions must be observed when deburring the end of a tube after it is cut?
Wall thickness must not be reduced in size or fractured
Describe the operation of quick disconnect couplings
Each half has a valve that is held open when coupled and is spring loaded closed when disconnected
Why are quick disconnect fittings used?
To provide a quick means to connect or disconnect a fluid line without loss of fluid or entrance of air into the system
How much slack must be left in a flexible hose during installation?
5-8% of the total hose length to allow for freedom of movement under pressure
What happens to the tube when a flareless fitting has been overtightened?
Tube is weakened when the nut drives the cutting edge of the sleeve too deeply into tube
What material should be selected for high pressure rigid fluid lines?
Annealed
1/4 hard corrosion resistant steel
What percentage of flattening is allowed when bending metal tubing?
25% max
Must maintain 75% of the original tube diameter
